Intergovernmental Panel on Climate Change
Liberals say that the United Nations' climate panel is "authoritative", but they never say what the basis of this "authority" is. They merely repeat their claim like the Nazi big lie technique. If you say something often enough, people eventually stop questioning it.
- The United Nations Intergovernmental Panel on Climate Change (IPCC), the world's most authoritative voice on the science of climate change, has stated unequivocally that global warming is happening and that human activity is the main driver. 
This claim, from Nature Canada, simply asserts that the IPCC is authoritative. We are to assume that since the UN has high ideals, it must be objective when it comes to scientific matters - as objective as it is when it comes to human rights issues. Clearly, this is misguided at best, and more likely a deliberate deception.
The UN is not neutral or impartial on anything. It takes whatever position its member states vote to take. Its positions either reflect a majority vote or a carefully crafted political compromise.
Just because a majority of government representatives assert something is so, does not make it so. They do not ask the scientists whose work they assess and summarize, to indicate whether they agree with the Summary for Policymakers. Indeed, twice now, the IPCC has released this political summary before releasing the scientific report it supposedly summarizes!